Structural basis of calcium-mediated conformational dynamics and cargo binding in vacuolar Sorting Receptor 1 (VSR1)

Calcium-dependent remodeling of inter-domain linkers in the VSR1 lumenal region exposes and remodels two cargo binding sites, with high calcium promoting binding and lower calcium plus pH favoring release.

• Why it matters: Cargo recognition and release by the N-terminal lumenal region of vacuolar sorting receptors remains unclear, limiting understanding of how VSR trafficking achieves accurate vacuolar cargo sorting during plant development.
• What they did: The authors solved crystal structures of unloaded and cargo-loaded VSR1 lumenal region (PA domain, Central domain, EGF-like repeats), then validated large conformational differences using SAXS and mapped solvent accessibility changes with XFMS.
• The result: Two cargo binding sites were identified (one in PA/Central and one in Central), and calcium coordination plus cargo binding drove solvent accessibility changes across all three domains, supporting a dynamic calcium- and pH-dependent sorting mechanism.

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